1. Field of the Invention
The present invention relates to a device of simple construction for preventing an erroneous start of a battery-powered vehicle.
2. Description of the Prior Art
A conventional erroneous start preventing device for a battery-powered vehicle, e.g., a fork lift truck, comprise a power supply, e.g., a battery, a key switch for turning the battery power supply on or off, a pair of switches: one (a forward motion switch) for directing the vehicle to move forward and the other (a rearward motion switch) for directing the vehicle to move rearward (the pair of switches not being simultaneously on), a pair of relays: a forward motion relay whose electromagnetic coil is energized and whose contacts are closed when the forward motion switch is turned on, and a rearward motion relay whose contacts are closed when the rearward motion switch is turned on, a neutral switch connected to the power key switch and interlocked with the forward and rearward motion switches to be deactivated (open) if either of the two switches is closed and activated only when both of the two switches are open, and a self-holding type relay whose coil is energized by the battery via the key switch when the neutral switch is activated and whose one pair of contacts A, connected to an erroneous operation indicating lamp, are in contact with each other to illuminate the lamp when the coil is not energized and another pair of contacts B, connected to a drive indicating lamp, are in contact with each other when the coil is energized.
In the above construction, when the key switch is turned on with the forward motion and rearward motion switches deactivated, the self-holding relay is actuated to bring the latter pair of contacts B described above in contact with each other since the neutral switch is closed. In this situation, the drive indicating lamp is lighted. Thereafter, when the forward motion or rearward motion switch is turned on for operating the vehicle to move the vehicle forward or rearward, the corresponding relay connects the motor to a DC power supply. At this time, the drive indicating lamp remains lighted by action of the self-holding relay although the neutral switch turned off because either of the forward motion and rearward motion switches is turned on.
When the key switch is turned on with either of the forward motion and rearward motion switches being turned on, the neutral switch is turned off so that, with the coil thereof being deenergized the self-holding relay is actuated to bring the pair of contacts A in contact with each other to light the erroneous operating jamp so that the erroneous starting of the batery-powered vehicle can be prevented.
However, such a conventional erroneous motion preventing device uses a neutral switch requiring a large volume of construction and a self-holding relay also requiring a large volume of construction, so that it is difficult to house the device within a limited space. Accordingly, the total cost of the device becomes high.